▎ 摘　　要

NOVELTY - Silicon-based-carbon composite comprises a core-shell structure. The core includes silicon, a silicon oxide compound and magnesium silicate. The shell includes first carbon layer and second carbon layer. The second carbon layer is reduced graphene oxide. USE - The silicon-based-carbon composite is useful in cathode material of lithium secondary battery (claimed). ADVANTAGE - The silicon-based-carbon composite improves the charge/discharge capacity, initial charge/discharge efficiency, and capacity retention rate of the secondary battery. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) preparing the silicon-based carbon composite, comprising obtaining silicon-silicon complex oxide in the core portion, crushing and classifying so that the average particle diameter of the silicon-silicon complex oxide of the core part is 3-15 mu m to obtain silicon-silicon complex oxide powder, forming first carbon layer on the surface of the silicon-silicon composite oxide powder, and forming second carbon layer on the surface of the first carbon layer to obtain core-shell structure composite; and (2) negative active material, comprising the silicon-based-carbon composite.